Huh? Prepare your child for a new step dad when they meet the guy she’s dating? Is she marrying them? I’m confused.

Anyone I’ve dated I’ve had the courtesy of alerting my ex that
Y D will be meeting them. He says “ok, cool, thanks” ( only 3
Guys in 12 years) and he married his affair partner. We do talk. We do Coparent.

You are speaking from a place of personal hurt, not from a place of wanting to coparent effectively